The present invention relates generally to methods and apparatus for treating injuries. More specifically, the present invention relates to methods and apparatus for the "cold therapy" and/or "heat therapy" of injuries. "Cold therapy" refers to the treatment of injuries such as sprains, knee injuries and the like by directly applying a cold substance (e.g. an ice pack) to the injured area. "Heat therapy" refers to treatment of the body and, more specifically, of muscle strains, stiffness, cramping and the like, by applying a source of heat to the affected part of the body.
In the case of cold therapy, for example, because the swelling associated with the above-described injuries begins almost immediately after the injury has occurred, treatment should begin promptly. Accordingly, it is desirable that whatever the source of cold therapy used for such treatment, the cold therapy source should be readily available, easy to use and capable of providing immediate and effective treatment to the injured area.
The most commonly used cold therapy devices are those that utilize ice as the cooling agent. Such devices typically include a waterproof container filled with ice. In general, the container is filled with ice, sealed and applied to the injured part of the body for a desired period of time. Such ice packs are described, for example, in U.S. Pat. Nos. 4,385,950 and 4,347,848. These patents describe a generally rectangular envelope with a waterproof interior bag located within the envelope. The envelope is open at one end for filling the waterproof interior bag with ice. After the interior bag has been filled with ice, the envelope is sealed and the ice pack applied to the injured area. Other similar ice packs are also described in U.S. Pat. No. 4,628,922 entitled "Knee Ice Pack," U.S. Pat No. 5,109,841 entitled "Facial Ice Pack," U.S. Pat. No. 4,951,666 entitled "Thermal Pack" and U.S. Pat. No. 5,336,426 entitled "Refillable Ice Pack."
The ice packs described above require a readily available supply of ice. If ice is not readily available, then a source of ice must be found and/or the ice transported to the site where the injury occurred. Often, a container that can store ice and keep it from melting must also be provided. Finding, transporting and storing ice makes using such ice packs more cumbersome and less convenient than desired.
Another drawback of using ice as the cooling agent is that stored ice from a freezer may be too cold for use in the "cold therapy" of injuries. For example, it is known that a temperature between approximately 32.degree.-50.degree. F. (0.degree.-10.degree. C.) is preferred for treating injuries of the type described above. Temperatures substantially below 32.degree. F. (0.degree. C.) are not recommended. Indeed, ice having a temperature substantially below 32.degree. F. can, if applied to the injured area for too long, cause frostbite. Ice from a freezer (or other storage container) may often be well below 32.degree. F. (0.degree. C.) and, therefore, too cold for use on an injury for an extended period of time. In addition, ice that is colder than desired may take longer to attain the preferred effective temperature range of 32.degree.-50.degree. F. (0.degree.-10.degree. C.), thereby delaying treatment.
In addition to the cold therapy devices that utilize ice as the cooling agent, the prior art also includes cold therapy devices that do not use ice but, instead, use a chemical reaction to produce the desired temperature for cold therapy. Such devices are commercially available from, for example, the assignee of the present application and are sold under the trade name, Kwik-Kold.RTM. and Kwik-Kold.RTM. Junior. U.S. Pat. No. 2,907,173 and U.S. Pat. No. 2,925,719 also describe cold therapy devices that utilize a chemical reactant that, when combined with another substance, produces an endothermic reaction and, thereby, reduces the temperature of the cold therapy device.
Cold therapy devices such as those commercially available or described in the above-identified patents are typically prepackaged, with an outer bag and an inner bag. The outer bag contains a chemical reactant such as ammonium nitrate and the inner bag contains water. Ammonium nitrate, when mixed with water, produces the known endothermic reaction ##STR1##
To initiate the endothermic reaction, the water-filled bag is ruptured so as to release the water into the interior of the outer bag. The mixing of water and the ammonium nitrate results in the above-identified endothermic reaction (i.e., the reaction takes energy, in the form of heat, from its surroundings.)
Alternatively, as set forth in the above-identified U.S. Pat. No. 2,907,173, a permanently sealed outer bag may contain two inner bags. A first porous inner bag contains the chemical reactant (e.g. ammonium nitrate) and the second inner bag contains water. Rupturing the second bag releases the water. The porous nature of the first bag (containing the ammonium nitrate) allows the released water to permeate the walls of the first bag, thereby causing the endothermic reaction described above.
U.S. Pat. No. 4,780,117 describes a cold pack wherein granular chemical reactants (e.g. ammonium nitrate) are encapsulated in a material that is at least partially soluble in a liquid. The encapsulated chemical reactant is placed in a first container. A second container filled with the liquid is also placed inside the first container and the first container is then sealed. The second container is physically ruptured to release the liquid. The liquid dissolves the coating applied to the reactant and mixes with the reactant to produce an endothermic reaction.
Finally, U.S. Pat. No. 3,950,158 describes a device that can be used for cold therapy or heat therapy. More specifically, this patent describes a "thermal pack" that includes a multi-bag system wherein a permanently sealed outer bag contains a chemical reactant (e.g. for cold therapy, urea with some ammonium chloride) and an inner bag contains water. To activate the thermal pack, the inner water-filled bag is ruptured to release water into the outer bag and produce a thermal reaction.
The cold therapy devices or thermal packs described above typically utilize an outer bag that is completely sealed. Accordingly, such bags are not reusable and must be disposed of after use. Moreover, because the cold therapy and/or thermal devices or packs are prepackaged with water or other liquid and the chemical reactant, they are heavier and, therefore, less portable and convenient than a device that is not prefilled with water.
Also, storage conditions may affect the performance of these types of devices. For example, in the case of cold therapy, if the entire prepackaged unit has been stored in a warm environment, the temperature of the water or other liquid contained within the inner bag may be higher than desired for the endothermic reaction. If the temperature of the water or liquid is too high, the endothermic reaction may not progress quickly enough or the temperature drop may not be sufficient to reach the desired temperature for cold therapy.
Accordingly, a general object of the present invention is to provide a thermal therapeutic device that does not suffer from the shortcomings described above. (As used herein, the term "thermal therapeutic device" is intended to be generic and include both cold therapy devices and/or heat therapy devices.) Another object of the present invention is to provide a thermal therapeutic device that is inexpensive, more convenient to use and that can, at least in part, be reused. Another object of the present invention is to provide a more lightweight and portable thermal therapeutic device that does not require the user to carry all of the components. A more particular object of the present invention is to provide a multi-container thermal therapeutic device in which one of the containers does not have to be manually ruptured to allow mixing of the contents. These and other objects are also found in the following description of the present invention.